This invention relates to the field of intravascular catheters and, more particularly, to a dilatation catheter for percutaneous transluminal coronary angioplasty (PTCA).
In PTCA procedures a guiding catheter having a preformed distal tip is percutaneously introduced into the patient's femoral artery by means of a conventional Seldinger technique and retrogradely advanced until the distal portion of the guiding catheter is located within the patient's ascending aorta with distal tip of the guiding catheter seated in the ostium of a desired coronary artery. The proximal end of the guiding catheter is torqued from outside the patient to guide distal tip of the guiding catheter into the desired ostium. A guidewire is positioned within an inner lumen of an dilatation catheter and then both are advanced through the guiding catheter to its distal end. The guidewire is first advanced out of the distal end of the guiding catheter into the patient's coronary artery until the distal end of the guidewire crosses a lesion to be dilated. Then the dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient's coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilation balloon is inflated with liquid one or more times to a predetermined size at relatively high pressures to expand the arterial passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the healthy artery wall on either side of the stenosis. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
Commercially available over-the-wire dilatation catheters for angioplasty and other vascular procedures usually comprise an elongated shaft with an inflatable dilatation member on a distal section of the shaft and an adapter on the proximal end of the shaft for the delivery of inflation fluid through an inner lumen extending through the catheter shaft to the interior of the inflatable dilatation member.
Over-the-wire dilatation catheters generally have relatively stiff proximal sections to provide pushability to the catheter shaft and relatively flexible distal sections to facilitate passing through tortuous coronary anatomy. The difference in mechanical property requirements between the proximal and distal sections of the catheter shaft usually requires the use of different materials, which in turn complicates the catheter manufacturing because the proximal and distal sections must be separately made and then secured together by heat or fusion bonding or a suitable adhesive. The difference in mechanical properties between the proximal and distal shaft sections also increases the difficulty in forming a smooth transition between the proximal and distal sections of the catheter shaft.
What has been needed is an easily manufactured dilatation catheter which has a relatively stiff proximal section for pushability, a very flexible distal section to facilitate advancement over a guidewire, i.e. trackability, within a patient's coronary anatomy and a smooth transition between the proximal and distal sections. The dilatation catheter of the present invention responds to these and other needs.